Formic acid production by simultaneous hydrothermal CO2 reduction and conversion of glucose and its derivatives

Synergistic Hydrothermal Conversion of Aqueous Solutions of CO2 and Biomass Waste Liquefaction into Formate

“…The main products were formic acid (FA), acetic acid (AA), and lactic acid (LA), which in experiments with NaHCO 3 that set alkaline conditions are present in the solution as the corresponding salts (sodium formate, acetate, and lactate). As indicated in the product chromatogram provided as supplementary information (Figure S2), additional products include glyceraldehyde, glycolaldehyde, and furfural, which in previous works have been identified as reaction intermediates in the transformation of bicarbonate with sugars produced by hydrolysis of cellulose/hemicellulose to FA, small amounts of non-hydrolyzed glucose and fructose, and also small concentrations of ethanol.…”

“…Previous studies have shown the capacity of different organic molecules to act as a CO 2 reductant under hydrothermal conditions. , A wide range of these molecules, in most cases obtained from lignocellulosic biomass, showed significant yields to formic acid (FA) when NaHCO 3 was added to the reaction medium, reaching yields up to 90% in the case of C3 alcohols, such as isopropanol and glycerol. , Further studies, including previous works of the authors, have investigated the origin of FA when using complex organic molecules, e.g., glucose and algae, as reductants, using marked NaH 13 CO 3 as the CO 2 source. These investigations showed that FA production resulted both from the NaH 13 CO 3 reduction (as determined by 13 C-NMR analyses) and from glucose decomposition. , It was also observed that both processes were synergistic in the sense that while on the one hand glucose and other organic derivatives acted as NaHCO 3 reductants, on the other hand the addition of NaHCO 3 , an oxidant, to the aqueous media enhanced the yield and especially the selectivity of the conversion of glucose to FA …”

“…8,9 It was also observed that both processes were synergistic in the sense that while on the one hand glucose and other organic derivatives acted as NaHCO 3 reductants, on the other hand the addition of NaHCO 3 , an oxidant, to the aqueous media enhanced the yield and especially the selectivity of the conversion of glucose to FA. 9 Thus, the optimization of the reaction may result in a process that achieves high yields to FA from both sources. The interest in the production of FA lies in the important role that it can play in the green hydrogen energy economy.…”

“…These investigations showed that FA production resulted both from the NaH 13 CO 3 reduction (as determined by 13 C-NMR analyses) and from glucose decomposition. 8,9 It was also observed that both processes were synergistic in the sense that while on the one hand glucose and other organic derivatives acted as NaHCO 3 reductants, on the other hand the addition of NaHCO 3 , an oxidant, to the aqueous media enhanced the yield and especially the selectivity of the conversion of glucose to FA. 9 Thus, the optimization of the reaction may result in a process that achieves high yields to FA from both sources.…”

“…21−24 In the presence of NaHCO 3 , these reducing organic compounds are oxidized to organic acids, while NaHCO 3 is converted as well into formate, thus promoting the global selectivity of the process toward acids. 9 Considering these antecedents, in this work, the hydrothermal liquefaction of lignocellulosic biomass waste samples (instead of the pure model organic compounds considered in previous studies) to organic compounds (particularly FA) and the hydrothermal reduction of NaHCO 3 (as a CO 2 source) to FA are performed simultaneously in a single process without intermediate steps of fractionation and purification. With this combination, the cumbersome and expensive intermediate steps of purification and separation of the organic reductants are avoided, and the use of energy is optimized because intermediate cooling and heating steps are also suppressed.…”